Wow, this is such a fun concept! It was really short but I enjoyed my time with it.
A few words of feedback:
1. Maybe keep up the normal game facade a bit longer before you introduce the completely new style.
2. The shooting part was kinda disorienting to move around since every few second you are on an other side of the cube
3. Half the time I couldn't see where the enemies were so I had to shoot at nothing hoping my bullets were hitting the guys. If you had more time to expand on this game adding indicators of where the enemies are would have been really useful.
Other then that, great job!